Dana Johnson
The main character. He finds a leftover egg monster in his backyard during his sister's birthday party, and he decides to bring it to a local scientist.
- Animal Lover: He once recalls how he found a turtle in his friend's backyard and decided to take care of him. When he finds an egg monster in the same area, he decides to bring him to Dr. Grey's laboratory for safety.
- Death by Adaptation: In Goosebumps HorrorTown, Gray has a skeleton in a freezer. After being asked about it, the designers for the game said it was Dana, this being a dark timeline.
- Disappointing Older Sibling: His sister, Brandy, does not think highly of him.
- Does Not Like Spam: While in Dr. Grey's lab, Dana is starving and demands food. He receives macaroni and cheese, to which he screams over and over that he hated it. Considering this is the only food that Dr. grey is giving him, Dana reluctantly eats it, even though he hated how it tasted.
- Gender-Blender Name: Yes, the name "Dana" is unisex, but very few males were named "Dana" in the 1990s.
- Gentleman and a Scholar: Despite being really smart for his age, he rarely, if ever, acts superior about it.
- I Hate Past Me: According to his friend Anne, he used to be a major fan of Teenage Mutant Ninja Turtles at the age of 10, wearing a t-shirt of them at school every day, and having a Ruth day party that was themed all about it. Dana himself is highly resentful of her bringing this up.
- Innocently Insensitive: When he finds the Martian egg, he wants to show Brandy his discovery. Brandy, who just had a humiliating birthday party involving a massive egg fight earlier that morning, is furious at Dana and slams her bedroom door in his face when he tries to show it to her.
- Nice Guy: He's a nice kid in general, and even cares about the egg monsters despite being grossed out by them.
- No Good Deed Goes Unpunished: He takes the egg monsters to Dr. Grey out of concern for their well being, only to find out Dr. Grey has other plans...
- Platonic Life-Partners: His best friend, Anne, lives next door to him, and he mentions how he's been best friends with her for many years.
- Shrinking Violet: He's a shy and nerdy but goodhearted kid.
- The Un-Favourite: His parents clearly prefer Brandy over him, mostly because she wins them over with her sweet attitude and batting eyelashes. Even Dana himself admits that he can't blame them.
Doctor Gray
A Mad Scientist who imprisons Dana and the egg monsters from Mars in his lab in order to experiment on them.
- Asshole Victim: He's presumably devoured by the Egg Monsters, but it's pretty hard to feel sad, given he was an abusive, hypocritical, murderous kidnapper.
- Big Bad: Of Egg Monsters From Mars.
- Bullying a Dragon: This guy not only imprisoned a group of potentially dangerous aliens in his freezer, but he also screams at and threatens the one human they've grown fond of. It doesn't end well for him.
- Humans Are the Real Monsters: You're led to believe at first that the egg monsters are the antagonists, but they turn out to be good and in fact save Dana from Dr. Grey. Then again, they did essentially rape him in his sleep.
- Hypocrite: Gray imprisons Dana for being in contact with the Egg Monsters. What he doesn't consider is that he's been in contact with them longer than this kid has, and that he wasn't even wearing gloves when taking Dana's specimen.
- Knight Templar: He insists that his kidnapping Dana is so that he can experiment on him for his and the rest of the planet's safety.
- No Body Left Behind: The egg monsters managed to devour Dr. Gray, whole, without leaving behind any traces. The following morning when Dana leads his parents back to the lab, the entire place is empty.
- Not-So-Well-Intentioned Extremist: Despite his claims above, he has no problem kidnapping and even murdering an innocent kid to keep his experiment safe, all the while ranting about how Dana ruined his work.
- Suspiciously Similar Substitute: Minus being a Serial Killer, Gray is a similar character to Mr. Toggle, as he's a sinister old Mad Scientist whose initially friendly before targeting the protagonist for his sick scientific curiosity. He also studies strange organisms in secret (Egg monsters in his case, cyborg hands in Toggle's) and eventually meets his demise when his test subjects revolt and allow his potential victim to escape.
- Villainous Breakdown: He completely loses it when he sees that the egg monsters have merged into a blanket in order to keep Dana warm.
- Would Hurt a Child: After his Villainous Breakdown, he threatens to freeze Dana to death for supposedly ruining his work.
The Egg Monsters
What comes first, the monster or the egg?
The eponymous monsters from the book's title. These critters are displaced from their home planet thanks to a solar storm, which sent them across the galaxy before landing on Earth in a meteor shower years ago. Dr. Gray is on a campaign to capture each and every single one of them for reasons unknown, and one of these monsters ending up in Dana's possession kicks off the story's plot.
They're considered as one of the more marketable monsters from the series (because they're just so darn adorable) back during the peak of Goosebumps' popularity in the 90s, featured in merchandise such as stickers, magic slime and colouring books.
- Adaptational Heroism:: In Goosebumps HorrorTown, their more ambiguously evilly traits are toned down and are portrayed as more heroic.
- Bizarre Alien Reproduction: They reproduce by impregnating any living things they covered, including humans, as Dana finds out at the end of the story.
- Blob Monster: Their default form, upon hatching, resembles "a yellow puddle with two beady black eyes". The cover art and subsequent merchandise fits their description perfectly.
- The Dog Bites Back: After being imprisoned for god knows how long by Dr. Gray, they finally broke out of the lab and the first thing they did is to devour Gray alive. Offscreen, though.
- Non-Malicious Monster: They're alien monsters who crash-landed on Earth years ago, merely acting on instincts to reproduce as all living creatures do.
- Shout-Out: They seem to be a G-rated homage to the titular creatures from the Alien films, in a way that their life cycle starts by hatching from eggs, ability to adapt in alien environments within short periods of time and reproducing by impregnating human beings.
- Zerg Rush: Justified, given their size where each of them can fit in a single egg, and at the end of the story a swarm of them managed to overpower Dr. Gray.
Brandy Johnson
Dana's younger sister. For her tenth birthday party, she is having an egg hunt, but it all goes awry when the guests find out that the eggs are highly breakable.
- Annoying Younger Sibling: Well, she isn't horrendous, but she can be a bit irritating towards Dana. He is constantly in her shadow, to which he dislikes. And after his whole tragedy involving the egg monsters, Brandy tells her friends all about it and how her brother's going crazy, much to his embarrassment as he overhead.
- Black Sheep: In a family consisting of people interested mostly in science, Brandy is the only one who does not partake in any of that.
- Break the Haughty: As soon as the party goes haphazard, Brandy starts shrieking at them to stop as it's her birthday, but gets hit with an egg herself while her guests laugh at her. And then her parents come out, to which her father starts yelling at her for not preventing this from happening, even though he mostly spoils her.
- Heavy Sleeper: Dana mentions that she is this, and this is why it took him so long to wake her up and show her the egg that he found.
- Jerkass Has a Point:
- Brandy was rightfully angry at her mother for not hard-boiling the eggs that were used for the birthday party. Her mother tries to argue, but stops herself as she realizes that her daughter is correct.
- She is also understandably furious at Dana for trying to show her an egg that night almost right after eggs were the subject matter that ruined her party.
- Knuckle Cracking: According to Dana, she does this when there are no adults around. And when the alien egg is cracking the morning after Dana discovers it, he initially thinks Brandy is doing this.
- My New Gift Is Lame: As part of the presents she got, Brandy's grandmother gave her a pair of fuzzy slippers and a pair of pajamas. Dana can tell that she doesn't like either of them, and she'll probably give the former to a dog as chew toys and she pretended to really enjoy the latter.
- Significant Green-Eyed Redhead: She has curly red hair and wide green eyes.
- Small Role, Big Impact: If Brandy didn't have her birthday party in her back yard, which had an egg theme going on, Dana would have likely never found the alien egg.
- Spoiled Brat: She gets everything she wants, and Dana believes that if she asks her parents for a red, white, and blue ostrich, they would give her one. She's not nearly as bad as Tara from The Cuckoo Clock of Doom, though.
